To provide an epoch-making waveguide type light beam controller with simple configuration which can be produced easily, and is very excellent in the performance.

An optical waveguide body in which a waveguide core 12 is formed in a clad layer 13 is made to coat an optical reaction layer 14 consisting of photo chromics material, optical diffraction structure 14a having the refractive index change generated repeatedly by irradiating the optical reaction layer 14 with the coherent lights 15 and 16 is formed, and the waveguide type light beam controller which controls the guiding waves of a waveguide core by the optical diffraction structure 14a is used as the waveguide type light beam controller S1.